This invention relates to a control device for controlling the mechanical printing elements of a matrix printer, which elements are arranged in a printing head moving along the print line and generate the characters to be printed by means of print dots, which dots are arranged in at least one predetermined printing raster, while a control unit generates a print signal for each printing element individually when this printing element reaches a position which lies a certain printing path before an envisaged printing location on an information carrier.
Matrix printers having a number of printing elements arranged in a printing head are generally known in a variety of versions, for example, from DE-PS 26 32 293, which corresponds to U.S. Pat. No. 4,010,835 Mar. 8, 1977. If printing is to take place in exactly defined locations on an information carrier, especially in the case of printing in both directions of movement of the printing head, the mechanical printing element must be triggered already before this location on the information carrier is reached, particularly in order to compensate for the printing time delay between triggering of the printing element, i.e. the printing needle driven by an electromagnet, and its moment of impact on the information carrier. During this needle stroke time the printing head has in fact moved over a certain distance which depends not only on the needle stroke time but also on the printing head speed. The compensation of the needle stroke time, therefore, can be achieved through a fixed lead time.
This is only true, however, if the printing head actually moves with constant speed. During the run-up at the beginning of a print line and the slow-down at the end of a print line (seen in the respective instantaneous direction of movement of the printing head), however, the printing head does not have its programmed speed so that the printing head requires an acceleration range and a deceleration path over which it is not printing. This leads to an increase in the dimensions of the overall matrix printer, and thus in the manufacturing cost, and to a decrease in the printing output.